| Falls in old adults are common and costly. The underlying causes of these falls often include various age-related physiological declines in sensory acuity, cognitive processing, and muscle function. This dissertation investigated how visual, cognitive and physical challenges can affect dynamic balance and muscle coordination in healthy old adults. A neuromodulation-based intervention to improve balance was also tested.;The first study investigated the relative effects of visual perturbations, attention-dividing cognitive tasks, and narrowed step width on dynamic balance during treadmill gait in healthy old and young adults. Balance was assessed by measuring step width and length variability over many strides. Compared to young adults, old subjects were very sensitive to visual perturbation in which a virtual hallway oscillated side-to-side. Under this condition, step width variability increased more than 150% relative to a normal condition. This result suggests that old adults increase their reliance on visual feedback for maintaining dynamic balance during walking.;The second study investigated the way aging affects modulation of lower extremity muscle coordination patterns when gait is challenged. Muscle activity was recorded from five muscles bilaterally with electromyography to evaluate coordination and co-activation. Contrary to some prior studies, muscle activation patterns for young and old adults in this study were similar during normal walking. However, the visual perturbation condition significantly increased muscle co-activation in old adults, both in comparison to normal walking and relative to young adults.;The final study used a double-blind randomized, controlled study to investigate the potential for cranial nerve non-invasive neuromodulation (CN-NINM) to improve gait and balance in old adults. CN-NINM may enhance neuroplasticity and prior studies suggest that coupling CN-NINM with gait and balance training may have therapeutic benefits in subjects with balance impairments. Active and control group subjects (8 each) participated in ten daily supervised gait and balance training sessions. Outcomes were assessed using clinical and quantitative metrics of dynamic and postural balance. Both groups showed significant improvement after training, though without differential benefit to the active group. Further study of CN-NINM in old adults with a history of falls is warranted, given their greater potential for improvement in balance. |
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